Cellulose acetate (CA) membranes have a very low binding affinity for most macromolecules
and are especially recommended for applications requiring low protein binding, such as
filtering culture media containing sera. However, both cellulose acetate and cellulose nitrate
membranes are naturally hydrophobic and have small amounts (less than 1%) of non-toxic
wetting agents added during manufacture to ensure proper wetting of the membrane. If
desired, these agents can be easily removed prior to use by filtering a small amount of warm
purified water through the membrane or filter unit. Surfactant-free cellulose acetate membranes
with very low levels of extractables are available on some Corning®
syringe filters.